gecko-dev/mobile/android/base/gfx/Layer.java

/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Android code.
 *
 * The Initial Developer of the Original Code is Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2009-2010
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Patrick Walton <pcwalton@mozilla.com>
 *   Chris Lord <chrislord.net@gmail.com>
 *   Arkady Blyakher <rkadyb@mit.edu>
 *
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 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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 * the provisions above, a recipient may use your version of this file under
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 * ***** END LICENSE BLOCK ***** */

package org.mozilla.gecko.gfx;

import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.Region;
import android.util.Log;
import java.nio.FloatBuffer;
import java.util.concurrent.locks.ReentrantLock;
import org.mozilla.gecko.FloatUtils;

public abstract class Layer {
    private final ReentrantLock mTransactionLock;
    private boolean mInTransaction;
    private Rect mNewPosition;
    private float mNewResolution;

    protected Rect mPosition;
    protected float mResolution;

    public Layer() {
        this(null);
    }

    public Layer(IntSize size) {
        mTransactionLock = new ReentrantLock();
        if (size == null) {
            mPosition = new Rect(0, 0, 0, 0);
        } else {
            mPosition = new Rect(0, 0, size.width, size.height);
        }
        mResolution = 1.0f;
    }

    /**
     * Updates the layer. This returns false if there is still work to be done
     * after this update.
     */
    public final boolean update(RenderContext context) {
        if (mTransactionLock.isHeldByCurrentThread()) {
            throw new RuntimeException("draw() called while transaction lock held by this " +
                                       "thread?!");
        }

        if (mTransactionLock.tryLock()) {
            try {
                return performUpdates(context);
            } finally {
                mTransactionLock.unlock();
            }
        }

        return false;
    }

    /** Subclasses override this function to draw the layer. */
    public abstract void draw(RenderContext context);

    /** Given the intrinsic size of the layer, returns the pixel boundaries of the layer rect. */
    protected RectF getBounds(RenderContext context) {
        return RectUtils.scale(new RectF(mPosition), context.zoomFactor / mResolution);
    }

    /**
     * Returns the region of the layer that is considered valid. The default
     * implementation of this will return the bounds of the layer, but this
     * may be overridden.
     */
    public Region getValidRegion(RenderContext context) {
        return new Region(RectUtils.round(getBounds(context)));
    }

    /**
     * Call this before modifying the layer. Note that, for TileLayers, "modifying the layer"
     * includes altering the underlying CairoImage in any way. Thus you must call this function
     * before modifying the byte buffer associated with this layer.
     *
     * This function may block, so you should never call this on the main UI thread.
     */
    public void beginTransaction() {
        if (mTransactionLock.isHeldByCurrentThread())
            throw new RuntimeException("Nested transactions are not supported");
        mTransactionLock.lock();
        mInTransaction = true;
        mNewResolution = mResolution;
    }

    /** Call this when you're done modifying the layer. */
    public void endTransaction() {
        if (!mInTransaction)
            throw new RuntimeException("endTransaction() called outside a transaction");
        mInTransaction = false;
        mTransactionLock.unlock();
    }

    /** Returns true if the layer is currently in a transaction and false otherwise. */
    protected boolean inTransaction() {
        return mInTransaction;
    }

    /** Returns the current layer position. */
    public Rect getPosition() {
        return mPosition;
    }

    /** Sets the position. Only valid inside a transaction. */
    public void setPosition(Rect newPosition) {
        if (!mInTransaction)
            throw new RuntimeException("setPosition() is only valid inside a transaction");
        mNewPosition = newPosition;
    }

    /** Returns the current layer's resolution. */
    public float getResolution() {
        return mResolution;
    }

    /**
     * Sets the layer resolution. This value is used to determine how many pixels per
     * device pixel this layer was rendered at. This will be reflected by scaling by
     * the reciprocal of the resolution in the layer's transform() function.
     * Only valid inside a transaction. */
    public void setResolution(float newResolution) {
        if (!mInTransaction)
            throw new RuntimeException("setResolution() is only valid inside a transaction");
        mNewResolution = newResolution;
    }

    /**
     * Subclasses may override this method to perform custom layer updates. This will be called
     * with the transaction lock held. Subclass implementations of this method must call the
     * superclass implementation. Returns false if there is still work to be done after this
     * update is complete.
     */
    protected boolean performUpdates(RenderContext context) {
        if (mNewPosition != null) {
            mPosition = mNewPosition;
            mNewPosition = null;
        }
        if (mNewResolution != 0.0f) {
            mResolution = mNewResolution;
            mNewResolution = 0.0f;
        }

        return true;
    }

    public static class RenderContext {
        public final RectF viewport;
        public final FloatSize pageSize;
        public final float zoomFactor;
        public final int positionHandle;
        public final int textureHandle;
        public final FloatBuffer coordBuffer;

        public RenderContext(RectF aViewport, FloatSize aPageSize, float aZoomFactor,
                             int aPositionHandle, int aTextureHandle, FloatBuffer aCoordBuffer) {
            viewport = aViewport;
            pageSize = aPageSize;
            zoomFactor = aZoomFactor;
            positionHandle = aPositionHandle;
            textureHandle = aTextureHandle;
            coordBuffer = aCoordBuffer;
        }

        public boolean fuzzyEquals(RenderContext other) {
            if (other == null) {
                return false;
            }
            return RectUtils.fuzzyEquals(viewport, other.viewport)
                && pageSize.fuzzyEquals(other.pageSize)
                && FloatUtils.fuzzyEquals(zoomFactor, other.zoomFactor);
        }
    }
}